I haven't heard anyone ding on her for the having the weight, just for wearing a bikini-thingy before her body was back in the right shape for it. From what was said on the radio, they offered her some less revealing, more flattering costume ideas, and she decided to ignore them, and hang out the lasagna belly. Sorry, but when you sing, dance, and lipsynch for a living, the standards are a little higher.
(BTW, if you dance AND lip-synch, at least do one well. I can accept bad dancing, and I can accept lip-synching on a TV appearance, but not both together[and I better not ever find out someone was lipsynching at a concert I paid for tickets to...])